PROJECT SUMMARY? PILOT PROJECT Feasibility and Safety of Vaginal Administration of 17-hydroxyprogesterone Caproate In this pilot study we are proposing to develop a vaginal formulation of 17-hydroxyprogesterone caproate (17- OHPC). We will first formulate a preparation of 17-OHPC that will be tested in rabbits to assure its tolerability. Once developed, we will determine how much of the compound enters the circulation. We will then test the formulation in non-pregnant women and measure the amount of medication reaching the blood. Once we have demonstrated that the preparation is well tolerated by women, we can the study the impact of the medication on those genes that respond to the progesterone hormone and eventually test the formulation in pregnant women who are now receiving this medication by injection. We postulate that the vaginal preparation will be better tolerated than injections and will be as effective if not more so.